WO2000006959A1

WO2000006959A1 - Storage container

Info

Publication number: WO2000006959A1
Application number: PCT/EP1999/003722
Authority: WO
Inventors: Vijay Mukund Naik; Vijay Ramakrishnan
Original assignee: Unilever Plc; Unilever N.V.; Hindustan Lever Limited
Priority date: 1998-07-29
Filing date: 1999-05-27
Publication date: 2000-02-10
Also published as: AU4371299A; JP2000043957A; GB9816549D0

Abstract

The invention relates to a thermally insulated container which retains the temperature of the objects stored in its inner cavity below 10 °C, said container comprising an outer shell of insulation and a continuous or segmented cooling surface, whereby the cooling surface causes 70-100 % encapsulation of the inner cavity.

Description

Storage Container

Technical Field of the Invention

The invention relates to improved low temperature containers for maintaining contents at temperatures below 10°C, even while the ambient temperature is very high.

Background to the Invention

Many perishable food items are transported / stored / distributed to consumers at sub - ambient temperatures, either to prevent their spoilage due to biological actions (as in the case of milk / fish / meat etc.) or to preserve their physical, olfactory and mouth - feel characteristics during consumption (soft drinks, frozen desserts, ice cream etc.). Containers of different types and sizes are employed for this purpose. They are thermally insulated to reduce the heat load on the stored articles. In addition, various means are employed to keep the contents of these containers cool by extraction of heat. For example, sometimes dry ice is added into the container to bring about this effect. Alternatively, one can use sealed bags / pads containing coolants to serve as "coolant batteries" for this purpose. Such coolant pads are pre - cooled or pre - frozen at a low enough temperature and packed along with perishable foods for maintaining them in the desired temperature range. The coolant pads may be loo^~se filled. Alternatively they

can be stacked along the vertical walls using a retainer device to improve accessibility of the stored food articles.

Sometimes, the coolant solutions are provided in jackets attached to the vertical walls of the insulated containers used for storing these food articles. The coolant may be sealed permanently within the fixed jackets. In such cases the coolant can be cooled on - line, continuously or intermittently by operating small refrigeration units permanently attached to the containers. Optionally, if the jacketed containers happen to be movable, they can be periodically taken to a service station for pre - cooling / freezing the coolant solution in the jackets / pads by coupling them temporarily to a central chilling / refrigeration unit.

The coolant is so chosen in such freezer cabinets generally used in retail sales of ice-creams, that it can be completely or partially frozen using the installed refrigeration unit and provides the necessary cooling effect for the contents. Even if there are temporary power interruptions, or if the cabinet is disconnected from the power supply and taken for distribution on a vehicle, the partially or fully frozen coolant continues to provide the cooling effect while the power is not available to the unit .

The container designs described above, however, have a drawback. The stored items cannot be maintained within the desired temperature range, for long enough time periods especially if the ambient temperatures are very high, unless the coolant / cooling surfaces are kept at e- temperatures well below the desired maximum temperature of the stored food articles. This necessitates use of an over - engineered refrigeration system and results in higher energy consumption. For e.g., in case of ice - cream, one would like to distribute the product near and below -18°C, for best results. The typical initial temperature of ice - cream at the time of loading into the container is -20°C. It is observed that under aggressive, hot ambient conditions as encountered in tropical countries, the temperature of ice - cream stored in containers described above rises quickly to over -18 °C, in spite of the presence of cooling pads or jackets. BR 9501576 discloses freezer cabinets designed for storage of frozen food stuffs by providing a eutectic material within the cabinets to maintain very low temperatures inside the jackets or pads. The recommended coolant temperatures were -27 °C and below for maintaining ice - cream at or below -18 °C for a reasonable length of time. In general, this is an impractical or expensive option in tropical countries where the ambient temperatures are relatively high and even small reduction in coolant temperature make excessive demands on the refrigeration systems specially when the source of electric power is erratic and expensive.

The object of the present invention is to provide a suitable container that can maintain its contents at temperatures below 10°C, in aggressive environmental conditions for longer periods of time, without recourse to inordinately low temperatures of cooling surfaces.

Another object of the present invention is to provide containers, particularly suited for transportation / storage / distribution of ice creams below and near -18°C over extended periods of time in aggressive environmental conditions, without recourse to inordinately low temperatures of cooling -surfaces .

The applicants have found that thermally insulated containers may be provided in which the temperature of contents are maintained below a desired . value for longer times, without recourse to excessively low temperatures of cooling surfaces by providing a continuous or segmented envelope of cooling surface with adequate coverage to the contents of the container. The applicants have found that optimum results may be obtained by providing a cooling surface which encapsulates the inner storage space of the container by about 70-100%. Accordingly, the invention relates to a thermally insulated container to retain the temperature of the objects stored in the inner cavity, below 10°C comprising an outer shell of insulation and a continuous or segmented cooling surface provided between the outer shell and the inner cavity causing a major or total encapsulation of the inner cavity.

According to a preferred aspect, the invention relates to a thermally insulated container to retain the temperature of the objects stored in the inner cavity, below 10°C comprising an outer shell of insulation and a continuous or segmented cooling surface provided between the outer shell and the inner cavity causing 70-100% encapsulation of the inner cavity.

According to a more preferred aspect, the invention relates to a thermally insulated container to retain the temperature of the objects stored in the inner cavity, below 10°C comprising an outer shell of insulation and a continuous or segmented cooling surface provided between the outer shell and the inner cavity causing 85-100% encapsulation of the inner cavity.

According to a preferred aspect the container is provided with an inner compartment defining a space between the outer shell and the inner compartment. When the inner compartment is provided the cooling surface is provided either in the said space between the outer shell and inner compartment or as an inside lining of the compartment.

The temperature of the cooling surface is preferably in the range 9°C to -45°C and more particularly 9°C to -30°C.

The cooling surface can be provided in various alternative forms such as thermally conducting (e.g. metallic) sheets attached to refrigerant coils or sealed jackets / detachable pads filled ^"with a coolant medium etc.

In a preferred embodiment of the invention, the coolant medium can be of any suitable composition such that the medium has a high heat absorption capacity of > 50 Joules / gram near and below the temperature range that the contents have to be preserved. In a more preferred embodiment of the invention, the coolant medium has a heat absorption capacity of > 50 Joules / gram in the temperature range of -18 and -30°C. In a still preferred embodiment of the invention, the coolant medium has a heat absorption capacity of > 120 Joules / gram between -18 and -30°C. It is further preferable to have a coolant composition which is foods compatible and with very low corrosivity towards commonly employed low cost materials used in the construction of containers. The coolant can be selected from refrigerant gases such as R-12, CARE 30, aqueous solutions of freezing point depressants or cryogenic mixtures or eutectic mixtures of salts and water.

It is preferred that the coolant jacket fully encapsulates the objects to be protected from heat exchange with the outside. The shape of the container can be a parallelepiped, cube, cylindrical or any other suitable design. It is preferred that all the walls of the freezer cabinet be lined with the coolant jacket such that it acts as a heat barrier between the stored objects and the outside atmosphere.

The coolant jackets and pads can be made from suitable material capable of withstanding low temperatures. The examples of suitable material are low carbon steel, stainless steel, galvanised iron, plastic, polymeric or other materials such as high, medium, or low density polyethylene, linear low density polyethylene, polyvinyl chloride, polycarbonate, polyester, metallic foil etc. It can be packaged in detachable/removable units of varying form, shape and size.

The principal and other objects of this invention and its advantages will now be described in greater detail with reference to non- limiting exemplary embodiments of the invention described hereunder . Examples :

Demonstration under vending conditions :

Six sets of test data were generated for containers of different designs used for the vending of ice-cream. The container was of 150 litre nominal capacity, 0.457m in height, 0.508 m in width and 0.660 m in^' length. The lid was 0.3m X 0.5 m in dimension. The container was insulated with ~ 75 mm PUF insulation (k ~ 25 mW / m K) . In all tests, the ambient temperature was 40 °C . The relative humidity of ambient air was 80 %. Ice Cream was loaded at -20°C. The lid of the container was opened for 90 seconds every 10 minutes and the temperatures of Ice Cream cones (Cornetto) in the container were noted over a period of 12 hours. The other parameters specific to each test were as given below.

Example 1 :

This was a container of conventional design with coolant jacket on four vertical walls enveloping ~ 62 % of the inner storage cavity, and containing an aqueous solution of sodium acetate with sodium benzoate being the major additive as the cooling medium. The coolant surface was maintained at -20 °C throughout the test. Example 2 :

This was a container of conventional design with coolant jacket on four vertical walls enveloping ~ 62 % of the inner storage cavity, and containing an aqueous solution of sodium acetate with sodium benzoate being the major additive as the cooling medium. The cooling surface area was increased by 50%, by filling in additional coolant pads in the storage cavity of the container along with the ice cream. Throughout the test the cooling surfaces of the jacket and the additional pads were maintained at -20 °C.

Example 3 :

This was a container of conventional design with coolant jacket on four vertical walls enveloping ~ 62 % of the inner storage cavity, and containing an aqueous solution of sodium acetate with sodium benzoate being the major additive-s- as the cooling medium.. The cooling surface area was increased by 100%, by filling in additional coolant pads in the storage cavity of the container along with the ice cream. Throughout the test the cooling surfaces of the jacket and the additional pads were maintained at -20 °C. Example 4 :

This was a container of conventional design with coolant jackets on four vertical walls enveloping ~ 62% of the inner storage cavity. The jackets contained a eutectic aqueous salt solution as the cooling medium. The cooling surface was maintained at -30 °C throughout the test.

Example 5 :

This was a container of conventional design with coolant jackets on four vertical walls enveloping ~ 62% of the inner storage cavity. The jackets contained a eutectic aqueous salt solution as the cooling medium. The cooling surface was maintained at -35 °C throughout the test.

Example 6:

This was a container of modified design with coolant jackets on all the walls of the cabinet and enveloping ~ 93% of the inner storage cavity containing an aqueous solution of sodium acetate with sodium benzoate being the major additive as the cooling medium. The coolant surfaces were maintained at -20°C throughout the test. Table 1

Examples 1 to 6 reveal that containers of improved design with coolant jackets maintained at -20 °C but completely or nearly completely enveloping the contents of the container gave the best results in retaining the ice-cream temperature below -18 °C in a 12 hour vending cycle. Increasing the cooling surface area by as much as 100% in a conventionally designed container by having additional loose filled coolant pads may not only increase the weight of the coolant but also would not be able to retain icecream temperature below -18 °C in a 12 hour vending cycle. The choice of a cooling jacket maintained at -35 °C is not practical and would not be economical because the power requirement for achieving lower and lower temperatures is significantly higher.

Demonstration under sealed conditions : Six sets of test data were generated for containers of different designs used for storage of ice-cream under sealed conditions. In the following Examples 7 to 12, the lid of the containers was kept closed during the test period and not subjected to opening and closing. The container was of 150 litre nominal capacity, 0.457m in height, 0.508 m in width and 0.660 m in length. The lid was 0.3m X 0.5 m in dimension. The container was insulated with ~ 75 mm PUF insulation (k ~ 25 mW / m K) . In all tests, the ambient temperature was 40 °C . The relative humidity of ambient air was 80 %. Ice Cream was loaded at -20 °C. The other parameters specific to each test were as given below.

Example 7: This was a container of conventional design with coolant jackets on the four vertical walls enveloping ~ 62% of the inner storage cavity. The jackets contained aqueous salt solution as the cooling medium. The coolant surface was maintained at -26 °C throughout the test. The temperatures of Ice Cream cones (Cornetto) in the container were noted over a period of 12 hours.

Example 8: This was a container of conventional design with coolant jackets on the four vertical walls enveloping ~ 62% of the inner storage cavity. The jackets contained aqueous salt solution as the cooling medium. The coolant surface was maintained at -27 °C throughout the test. The temperatures of Ice Cream cones (Cornetto) in the container were noted over a period of 12 hours.

Example 9: This was a container of conventional design with coolant jackets on the four vertical walls enveloping ~ 62% of the inner storage cavity. The jackets contained aqueous salt solution as the cooling medium. The coolant surface was maintained at -36 °C throughout the test. The temperatures of Ice Cream cones (Cornetto) in the container were noted over a period of 50 days.

Example 10: This was a container of conventional design with coolant jackets on the four vertical walls enveloping ~ 62% of the inner storage cavity. The jackets contained aqueous salt solution as the cooling medium. The coolant surface was maintained at -37 °C throughout the test. The temperatures of Ice Cream cones (Cornetto) in the container were noted over a period of 50 days.

Example 11: This was a container of modified design with coolant jackets on and enveloping 93% of the inner storage cavity. The jackets contained an aqueous solution of sodium acetate and sodium benzoate as the cooling medium. The coolant surface was maintained at -20 °C throughout the test. The temperatures of Ice Cream cones (Cornetto) in the container were noted over a period of 50 days.

Example 12: This was a container of modified design with coolant jackets on and enveloping 100% of the inner storage cavity. The jackets contained an aqueous solution of sodium acetate and sodium benzoate as the cooling medium. The coolant surface was maintained at -20 °C throughout the test. The temperatures of Ice Cream cones (Cornetto) in the container were noted over a period of 50 days.

Table II

Examples 7 and 8 show that a cooling surface temperature of -27 °C or below is required in a container of conventional design with 62% coverage of the storage cavity, to retain the ice creams below -18 °C for a period of 12 hours even if the lid is kept closed throughout the 12 hour period. Similarly, examples 9 and 10 show that a cooling surface temperature of -37 °C or below is required in a container of conventional design with 62% coverage of the storage cavity, to retain the ice creams below -18 °C for a period of 50 days if the lid is kept closed throughout the 50 day period.

On the other hand, examples 11 and 12 show that in a container of modified design providing 93% to 100% encapsulation of the storage cavity by the cooling surface, is able to retain the ice creams below -18 °C for a period of 50 days if the lid is kept closed throughout the 50 day period even though the cooling surface is maintained at -20 °C which is far above the cooling surface temperatures required in examples 7 to 10.

This improvement in the retention of ice-creams in the region of the desired temperature of -18 °C, even though the cooling surface is maintained at a relatively high temperature of -20 °C by ensuring that the cooling surfaces provide a 70 to 100 % envelope around the storage cavity for the ice-cream is remarkable and unexpected.

Claims

1. A thermally insulated container to retain the temperature of the objects stored in the inner cavity below 10┬░C, said container comprising an outer shell of insulation and a continuous or segmented cooling surface, whereby the cooling surface causes 70-100% encapsulation of the inner cavity.

2. A container according to claim 1, wherein the cooling surface causes 85-100% encapsulation.

3. A container according to claim 1 or 2 wherein the temperature of the cooling surface is from 9 to -30┬░C, more preferred -10 to -30┬░C.

4. A container according to claims 1-3 wherein the cooling surface is formed of detachable cooling pads filled with a cooling medium.

5. A container according to claims 1-3 wherein the cooling surface is formed of thermally conducting sheets attached to refingerant cools.

6. A container according to claims 1-5, said container being free of a electricity supply or other power connection.